How to Test Dishwasher Thermostat

A dishwasher that fails to heat water properly can leave you with dirty dishes and a sense of frustration. Often, the culprit behind this issue is a faulty thermostat, a small but vital component responsible for regulating water temperature.

Testing the thermostat is a straightforward diagnostic task that can save you from an expensive service call and help you understand your appliance better. This guide on how to test dishwasher thermostat will walk you through the process, empowering you to identify the problem with confidence.

Tackling this DIY project requires a bit of preparation and a focus on safety, but it’s well within the reach of most homeowners. By following a clear, step-by-step process, you can determine if the thermostat is the source of your dishwasher woes. Whether your dishes are coming out greasy, spotted, or still dirty, checking the thermostat is a critical first step in troubleshooting heating issues and restoring your dishwasher to its full cleaning power.

Tools and Materials You’ll Need

• Screwdriver set (Phillips and flathead)
• Nut driver set or adjustable wrench
• Multimeter (digital or analog)
• Needle-nose pliers
• Work gloves
• Safety glasses
• Towels or rags
• Flashlight or headlamp
• Owner’s manual for your dishwasher model (optional, but helpful)

8 Simple Step-By-Step Guidelines on How to Test Dishwasher Thermostat

Step 1: Disconnect the Dishwasher from Power and Water

Safety is the absolute priority before beginning any appliance repair. You must completely disconnect the dishwasher from its power source to eliminate the risk of electric shock. The easiest way to do this is to locate the circuit breaker that controls the dishwasher in your home’s main electrical panel and switch it to the “OFF” position.

For added safety, you can unplug the dishwasher from the wall outlet, which is typically located under the sink or behind the unit itself. If the dishwasher is hardwired directly into your home’s electrical system, relying on the circuit breaker is the correct procedure.

Once the power is off, you also need to shut off the water supply. The shut-off valve is usually located under the kitchen sink and is connected to the hot water line. Turning this valve clockwise will stop the flow of water to the dishwasher.

Place a few towels on the floor in front of the dishwasher to absorb any water that may spill during the process. Taking these initial safety measures is non-negotiable and ensures a secure environment for you to work in. It’s a good practice to double-check that the power is off by trying to turn on the dishwasher from its control panel; if it remains unresponsive, you’re ready to proceed.

Step 2: Access the Dishwasher’s Internal Components

With the power and water safely disconnected, you need to gain access to the thermostat. In most dishwasher models, the thermostat and other key electrical components are located behind the main access panel at the bottom front of the unit. This panel is usually held in place by two or four screws.

Use your screwdriver or nut driver to remove these screws, setting them aside in a safe place so you don’t lose them. Gently pull the access panel away from the dishwasher. You may also need to remove a separate toe-kick panel located right at floor level.

Once the panel is removed, you will have a clear view of the dishwasher’s underbelly, including the motor, pump, water inlet valve, and various wiring. The thermostat is typically a small, round or rectangular component mounted on the underside of the dishwasher tub or near the heating element. It will have two wires connected to it.

Using a flashlight will help you get a better look and correctly identify the thermostat among the other parts. Referencing your dishwasher’s owner’s manual or an online diagram for your specific model can be very helpful if you are unsure which component is the thermostat.

Step 3: Locate and Identify the Thermostat

Now that you have access to the dishwasher’s mechanical parts, your next task is to pinpoint the exact location of the thermostat. The most common location is on the bottom of the tub, near the center or close to where the heating element enters the tub.

The heating element is a thin, circular metal tube that heats the water, and the thermostat works in tandem with it. Look for a small, disc-shaped part with two electrical terminals where wires are connected. It’s often held in place by a metal clip or a small bracket.

Sometimes there are two thermostats: a high-limit thermostat that acts as a safety device to prevent overheating, and an operating thermostat that regulates the main wash and rinse temperatures. The high-limit thermostat is usually mounted directly on the heating element assembly, while the operating thermostat is on the tub. Your goal is to test the primary operating thermostat.

If you see multiple similar-looking components, consult your dishwasher’s technical sheet or search for your model number online to find a diagram that clarifies the part’s identity and location. Correctly identifying it is crucial for an accurate test.

Step 4: Disconnect the Wires from the Thermostat

Before you can test the thermostat for continuity, you must carefully disconnect the two wires attached to its terminals. These wires are usually connected with simple slip-on connectors. Grasp each connector firmly and pull it straight off the terminal. If they are tight, you can use needle-nose pliers to gently wiggle them free. Be careful not to pull on the wires themselves, as this could damage the wire or the connector, leading to another repair.

Inspect the connectors and the wire ends for any signs of corrosion, burning, or damage. A loose or corroded connection can also cause heating problems, so it’s a good thing to check while you are there. If the connectors look dirty or corroded, you can clean them with a small wire brush or contact cleaner. After disconnecting the wires,

bend them slightly out of the way so they don’t accidentally touch any metal parts or interfere with your multimeter probes during the test. This step isolates the thermostat electrically, ensuring your multimeter reading only reflects the state of the thermostat itself.

Step 5: Set Up Your Multimeter

Your multimeter is the key tool for this diagnostic test. Whether you have a digital or analog model, the setup is similar. You need to set the multimeter to test for continuity, which is often indicated by an icon that looks like a sound wave or a diode symbol. On some meters, you will use the lowest setting in the ohms (Ω) resistance mode. The continuity setting is ideal because it provides a clear audible beep if an electrical circuit is complete, making the test foolproof.

Before testing the thermostat, test your multimeter to ensure it’s working correctly. Turn it to the continuity or ohms setting and touch the two metal probes together. If the multimeter is working, a digital model should display a reading close to zero and emit a continuous beep.

An analog meter’s needle should swing all the way to the right (zero ohms). If your meter does not respond this way, check its batteries or settings before proceeding. This simple check confirms your tool is reliable and that any reading you get from the thermostat will be accurate.

Step 6: Test the Thermostat for Continuity

With the multimeter ready, it’s time to test the thermostat. The thermostat is essentially a switch that should be closed when cold, allowing electricity to flow to the heating element. At room temperature, a functional thermostat should show continuity. Touch one of your multimeter’s probes to one of the thermostat’s metal terminals and the other probe to the second terminal.

The polarity of the probes does not matter for this test. Hold the probes firmly against the terminals to ensure a good connection. If the thermostat is working correctly, the multimeter should immediately beep or show a reading of zero or very close to zero ohms. This indicates a closed circuit, meaning electricity can pass through it as designed when the dishwasher is cold.

If the multimeter does not beep and the display continues to show “OL” (open loop), “1,” or infinity, it means there is no continuity. This indicates the thermostat is faulty and stuck in the open position, preventing the heating element from receiving power. An open circuit means the thermostat is broken and needs to be replaced.

Step 7: Perform a Secondary Test (If Necessary)

While a room-temperature continuity test is usually sufficient, some thermostats can fail intermittently when they heat up. If your initial test showed continuity but you still suspect the thermostat, you can perform an additional test involving heat. This step should be done with extreme caution.

Carefully remove the thermostat from the dishwasher; it is usually held by a clip or a couple of screws. Hold the thermostat with pliers (not your fingers) and briefly and carefully heat it with a hairdryer or heat gun. The goal is to raise its temperature above its activation point.

As the thermostat heats up, the internal switch should open, breaking the electrical circuit. Test it again with the multimeter while it is still warm. A functioning thermostat should now show no continuity (an open circuit).

If it still shows continuity even when hot, it means the switch is fused closed and it needs to be replaced. Conversely, once you remove the heat and let it cool down, continuity should be restored. This more advanced test confirms the thermostat’s ability to open and close the circuit at the correct temperature range.

Step 8: Reassemble the Dishwasher

Once you have completed your tests and determined whether the thermostat needs replacement, it’s time to put everything back together. If the thermostat was faulty, install the new one by securing it in place and reconnecting the wires. If the original thermostat tested fine, reconnect the wires to its terminals, ensuring the connectors are snug. Carefully slide the dishwasher back into its position under the counter if you had to pull it out.

Next, reattach the lower access panel and toe-kick, securing them with the screws you set aside earlier. Be careful not to overtighten the screws. Once the panels are secure, you can restore the water and power.

Turn the water supply valve counter-clockwise and then switch the circuit breaker back to the “ON” position. Run a short test cycle on your dishwasher to ensure everything is working correctly and to check for any leaks. If the thermostat was the problem, you should now enjoy properly heated water and sparkling clean dishes.

Following these steps on how to test dishwasher thermostat, you can save both time and money by troubleshooting the issue on your own.

Conclusion

Testing your dishwasher’s thermostat is a manageable task that can diagnose one of the most common reasons for poor cleaning performance. By methodically following the steps on how to test dishwasher thermostat to safely access, test, and evaluate this small but important part, you can avoid guesswork and unnecessary expenses. The process not only helps you pinpoint the problem but also builds your confidence in handling basic appliance repairs.

Whether your test reveals a faulty thermostat or confirms it’s working properly, you have made significant progress in troubleshooting your dishwasher. Armed with this knowledge, you are better prepared to either replace the part yourself or have an informed conversation with a professional technician. Ultimately, taking the time to perform this check ensures your dishwasher can continue to operate efficiently, providing you with the sparkling clean dishes you expect.